This invention relates to directly paintable thermoplastic olefin compositions comprising an epichlorohydrin rubber; said compositions have improved electrical conductivity and therefore are particularly suitable to electrostatic painting. The TPO compositions of the invention are useful for making injection molded parts, such as automobile bumpers, and exhibit excellent paint adhesion and durability.
Thermoplastic olefins (TPOS) are uncrosslinked blends of olefin polymers and polyolefin elastomers. They can be made by physically blending in an internal mixer, or by polymerizing in a reactor. These materials are not paintable or coatable, because the paints or coatings consist of polar materials like urethanes, acrylics, epoxies, or melamines that have very poor adhesion to non-polar materials like polyolefins. Typically an adhesion promoter is used as the tie layer between the TPO substrate and the paint coating. This extra step adds to the cost of the product, and the coating is not very durable.
U.S. Pat. No. 5,962,573 discloses a directly paintable polymer composition comprising: (1) a thermoplastic olefin, (2) a propylene homopolymer or a propylene copolymer with ethylene or a C4-8 xcex1-olefin, grafted with an anhydride of an aliphatic xcex1,xcex2-unsaturated dicarboxylic acid; (3) an oxidized polyethylene wax having a melting point of less than 116xc2x0 C. and an acid number of less than 40; (4) a functionalized polymer that is reactive with the anhydride groups of the grafted polymers and, optionally, (5) a polyolefin rubber grafted with an anhydride of an aliphatic xcex1,xcex2-unsaturated dicarboxylic acid, and (6) an ethylene polymer grafted with an anhydride of an aliphatic xcex1,xcex2-unsaturated dicarboxylic acid.
Injections molded parts such as automobile bumpers made from this composition are directly paintable with polar paints or coatings without the need for a layer of adhesion promoter between the thermoplastic olefin surface and the paint, and exhibit good paint adhesion an durability.
An important parameter in the paint process is the efficiency of the paint being sprayed; in fact, since the paint is airborne, some of it does not arrive onto the part to be treated and some is lost in the environment. Electrostatic painting of substrates tends to reduce paint waste and emissions, as compared to non-electrostatic painting techniques.
Electrostatic painting techniques require the substrate to be electrically conducting and common TPOs for injection molded articles are electrically insulating; one of the methods to solve this problem, according to the prior art, consists in applying an electrically conductive primer prior to painting, in order to display an increased paint transfer efficiency. Nevertheless, this further step is costly and time consuming.
An alternative technique is to use a grounding clip, but this causes higher film buildup near the grounding clip with film buildup decreasing as the distance from the grounding clip increases. In addition, after several passes through the paint spraying booth, significant resistance to ground may be encountered due to multiple paint layers on the substrate itself
A further way of improving the electrical conductivity is to incorporate additives, such as stainless steel fibers, into the thermoplastic polymer itself; nevertheless said additives are not suitable for TPO-based compositions because they lead to a degradation of their desirable mechanical properties, such as impact strength and tensile elongation. Moreover, said additives significantly increase the brittleness of such TPO compositions.
U.S. Pat. No. 5,484,838 describes thermoplastic olefin compositions having improved electrical conductivity due to the addition of electrically conductive carbon black; in these compositions, at least a portion of the carbon black has to be dispersed within the crystalline polymer component of the TPO. Nevertheless, carbon black or additives of similar nature are difficult to handle and, as a consequence. their exact dispersion and the morphology needed for the TPO matrix are very difficult to control.
In addition, conductive carbon black may cause a reduction in the effectiveness of the directly paintable functionalized polymers, presumably by absorbing the materials onto the surface of the carbon black itself.
Thus, there is still a need for a TPO composition having an improved electrical conductivity and therefore allowing a better paint efficiency, at the same time meeting the stringent requirements for paint adhesion and durability of today""s marketplace, particularly in the automotive industry.
The composition of the present invention comprises, by weight:
(1) 100 parts of a thermoplastic olefin comprising an olefin polymer having an isotactic index of at least 80 and an olefin polymer rubber, the thermoplastic olefin having a rubber content of at least 20%;
(2) about 5 to about 20 parts per hundred parts of the thermoplastic olefin of a propylene homopolymer or propylene copolymer with ethylene or a C4-8 xcex1-olefin having an ethylene or xcex1-olefin content of about 0.5% to about 20%, grafted with an anhydride of an aliphatic xcex1,xcex2-unsaturated dicarboxylic acid and having an anhydride content of about 2% to about 5%;
(3) about 3 to about 20 parts per hundred parts of the thermoplastic olefin of an oxidized polyethylene wax having a melting point of less than 116xc2x0 C. and an acid number of less than 40;
(4) a functionalized polymer that is reactive with the anhydride groups of the grafted polymers, selected from the group consisting of:
(a) about 2 to about 6 parts per hundred parts of the thermoplastic olefin of an amine-terminated polyalkylene glycol;
(b) about 2 to about 6 parts per hundred parts of the thermoplastic olefin of a hydroxy-terminated polyolefin;
(c) about 2 to about 6 parts per hundred parts of the thermoplastic olefin of a hydroxy-terminated polybutadiene;
(d) about 2 to about 8 parts per hundred parts of the thermoplastic olefin of a hydroxy-terminated olefin/alkylene oxide copolymer;
(e) about 2 to about 8 parts per hundred parts of the thermoplastic olefin of a hydroxy-terminated polyalkylene oxide;
(f) about 2 to about 8 parts per hundred parts of the thermoplastic olefin of a methoxy-terminated polyalkylene oxide;
(g) about 2 to about 8 parts per hundred parts of the thermoplastic olefin of an amine-terminated olefin/alkylene oxide copolymer, and
(h) mixtures thereof;
(5) about 2 to about 20 parts per hundred parts of the thermoplastic olefin of an epichlorohydrin rubber;
(6) optionally, about 5 to about 30 parts per hundred parts of the thermoplastic olefin of a polyolefin rubber grafted with an anhydride of an aliphatic xcex1,xcex2-unsaturated dicarboxylic acid, having an anhydride content of at least 0.3% but less than 3% and comprising a polymer of ethylene and a C3-8 xcex1-olefin, optionally containing about 0.5% to about 10% of a diene, having an ethylene content of about 30% to about 70%;
(7) optionally, about 5 to about 20 parts per hundred parts of the thermoplastic olefin of an ethylene polymer grafted with an anhydride of an aliphatic xcex1,xcex2-unsaturated dicarboxylic acid, having an anhydride content of about 1% to about 16% and a number average molecular weight Mn of about 500 to about 5000, provided that at least 5 parts of anhydride-grafted polypropylene or propylene copolymer and 3 parts of oxidized polyethylene wax per hundred parts of the thermoplastic elastomer are also present;
(8) optionally, about 5 to about 20 parts per hundred parts of the thermoplastic olefin of a thermoplastic resin selected from the group consisting of:
(a) an hydrogenated polymer consisting essentially of terpene hydrocarbons, having a drop softening point greater than about 70xc2x0 C., and a number average molecular weight Mn greater than about 500; and
(b) an hydrogenated polymer of styrene or alkyl-substituted styrene, having a number average molecular weight Mn ranging between about 600 and about 20,000; and
(9) optionally, about 0.1 to about 5 parts per hundred parts of the thermoplastic olefin of an organic sulfonic acid salt of a group I or II metal of the Periodic Table of the Elements (IUPAC version).
Injection molded parts, such as automobile bumpers, made from this composition have an increased conductivity and are particularly suitable for electrostatic painting. Such parts are directly paintable with polar paints or coatings with much higher paint efficiency with respect to the prior art compositions, molded parts do not require the use of a layer of adhesion promoter between the thermoplastic olefin surface and the paint, and exhibit excellent paint adhesion and durability.
Moreover, with respect to the compositions of the prior art, as described in U.S. Pat. No. 5,484,838, the composition of the invention does not display the problems associated with the use of carbon black, since epichlorohydrin rubbers are easy to handle and can be readily dispersed in the TPO matrix.
Finally, the addition of an epichlorohydrin rubber to the TPO composition does not alter the favorable mechanical properties of the composition itself.
A further object of the present invention is a molded thermoplastic article comprising a composition as described above, and more particularly a molded thermoplastic automotive article comprising a composition as described above.
Component (1) of the composition of this invention is a thermoplastic olefin comprising a crystalline olefin polymer and an olefin polymer rubber, the thermoplastic olefin having a rubber content of at least 20%. Suitable thermoplastic olefins include, for example,
(a) a composition comprising, by weight,
(i) about 10% to about 60%, preferably about 20% to about 50%, of a propylene homopolymer having an isotactic index greater than 90, preferably between 95 and 98, or a crystalline propylene copolymer with ethylene and/or a C4-8 xcex1-olefin having a propylene content greater than 85% and an isotactic index of greater than 85;
(ii) about 30% to about 60%, preferably about 30% to about 50%, of an amorphous ethylene-propylene or ethylene-butene copolymer, optionally containing about 1% to about 10% of a diene, which is xylene soluble at room temperature and has an ethylene content of about 30% to about 70%;
(iii) about 2% to about 20%, preferably about 7% to about 15%, of a semi-crystalline ethylene-propylene or ethylene-butene copolymer that is xylene insoluble at room temperature and has an ethylene content of greater than 75% but less than 92%; and
(iv) about 5% to about 20%, preferably about 7% to about 15%, of an ethylene polymer having a density of 0.91 to 0.96 g/cm3 and a melt index of 0.1 to 100 g/10 min, preferably about 15 to about 50 g/10 min. Ethylene homopolymer is preferred. However, copolymers containing 8% or less of an xcex1-olefin comonomer can also be used.
(b) a composition comprising, by weight:
(i) about 20% to about 70%, preferably about 50% to about 70%, of a crystalline propylene homopolymer having an isotactic index greater than 90, preferably between 95 and 98, or a crystalline propylene copolymer with ethylene and/or a C4-8 xcex1-olefin having a propylene content greater than 85% and an isotactic index of greater than 85;
(ii) about 20% to about 75%, preferably about 30% to about 50%, most preferably about 30% to about 35%, of an amorphous copolymer of ethylene selected from the group consisting of (1) ethylene/propylene, (2) ethylene/butene-1, (3) ethylene/octene-1, and (4) mixtures thereof, optionally containing about 1% to about 10%, preferably about 1% to about 4%, of a diene, which is xylene soluble at room temperature and has an ethylene content of about 30% to about 70%, preferably about 40% to about 60%; and
(iii) about 2% to about 30%, preferably about 2% to about 10%, most preferably about 2% to about 5%, of a semi-crystalline copolymer of ethylene selected from the group consisting of (1) ethylene/propylene, (2) ethylene/butene-1, (3) ethylene/octene-1, and (4) mixtures thereof, which is xylene insoluble at room temperature and has an ethylene content of greater than 90%;
(c) a composition comprising, by weight,
(i) at least one heterophasic polyolefin composition comprising:
(1) about 90% to about 55% of a propylene polymer material selected from the group consisting of a propylene homopolymer having an isotactic index greater than 90, and a crystalline copolymer of propylene and an xcex1-olefin of the formula CH2xe2x95x90CHR, where R is H or C2-C6 alkyl, the xcex1-olefin being less than 10% of the copolymer, and
(2) about 10% to about 45% of an elastomeric copolymer of propylene and an xcex1-olefin of the formula CH2xe2x95x90CHR, where R is H or C2-C6 alkyl, the xcex1-olefin being about 50% to about 70% of the elastomeric copolymer, and about 10% to about 40% of the elastomeric copolymer being insoluble in xylene at ambient temperature, and
(ii) about 5 to about 50 parts, preferably about 10 to about 30 parts, and most preferably about 10 to about 25 parts, per hundred parts of (c)(i) of an elastomeric copolymer of ethylene and a C3-8 xcex1-olefin made with a metallocene catalyst. If more than one heterophasic polyolefin (c)(i) is present, the heterophasic polyolefins can be combined in any proportion.
(d) a composition comprising, by weight:
(i) about 30% to about 50%, preferably about 35% to about 45%, of a propylene homopolymer having an isotactic index greater than 90, and
(ii) about 70% to about 50%, preferably about 65% to about 55%, of an olefin polymer composition comprising:
(1) about 25% to about 50% of a crystalline propylene homopolymer with a solubility in xylene at room temperature of less than or equal to 4%, or a crystalline copolymer of propylene with ethylene or a C4-8 xcex1-olefin having an ethylene or xcex1-olefin content of about 0.5% to about 3%, and a solubility in xylene at room temperature of less than or equal to 4%, and
(2) about 50% to about 75% of an amorphous copolymer of ethylene and a C4-8 xcex1-olefin, wherein the xcex1-olefin content is about 10% to about 20%, and the copolymer is about 10% to about 40% soluble in xylene at room temperature; and
(e) a composition comprising, by weight:
(i) about 80% to about 30%, preferably about 70% to about 50%, of a propylene homopolymer having an isotactic index greater than 90, and
(ii) about 20% to about 70%, preferably about 30% to about 50%, of an elastomeric copolymer of ethylene and a C3-8 xcex1-olefin, optionally containing about 1% to about 10%, preferably about 1% to about 4%, of a diene, and having an ethylene content of about 30% to about 70%, preferably about 40% to about 60%.
Thermoplastic olefins (a) and (c) are preferred.
Thermoplastic olefins (a) and (b) and compositions (c)(i) and (d)(ii) are typically prepared by sequential polymerization in at least two stages. Alternatively, the components can be prepared separately and then blended together by melt-kneading or melt blending. The polymerization conditions and the polymerization catalyst are described in more detail in U.S. Pat. Nos. 5,143,978; 5,302,454; 5,360,868; and 5,486,419, which are incorporated herein by reference. Sequential polymerization is preferred.
For TPO (a), (i) can be made in the first reactor, (ii) and (iii) in the second reactor, and (iv) in the third reactor. Alternatively, (iv) can be made in the second reactor and (ii) and (iii) in the third reactor.
For TPO (b), (i), (ii), and (iii) are preferably formed in a reactor or series of reactors in at least two stages by first polymerizing propylene to form (i) and then polymerizing ethylene and propylene, butene-1, or octene-1, or mixtures thereof, in the presence of (i) and the catalyst used in the first stage to form (ii) and (iii). The polymerization can be conducted in the liquid or gas phase or in liquid-gas phase.
For TPO (b), (i) can be prepared using a Ziegler-Natta catalyst or a mixture of Ziegler-Natta and metallocene catalysts. Components (ii) and (iii) can be prepared using Ziegler-Natta or metallocene catalysts or a combination of the two, with one type of catalyst being used for one stage and the other type of catalyst being used for the next stage when the TPO is made by sequential polymerization.
The C4-8 xcex1-olefins useful in the preparation of the thermoplastic olefins include, for example, butene-1; pentene-1; hexene-1; 4-methylpentene-1, and octene-1.
The diene, when present, is typically a butadiene; 1,4-hexadiene; 1,5-hexadiene, or ethylidenenorbornene.
Component (2) is a propylene homopolymer or propylene copolymer with ethylene or a C4-8 xcex1-olefin, grafted with an anhydride of an aliphatic xcex1,xcex1-unsaturated dicarboxylic acid and having an ethylene or xcex1-olefin content of about 0.5% to about 20%, preferably about 1% to about 10%, and most preferably about 1% to about 5%. The polymer has an anhydride content of about 2% to about 5%, preferably about 3% to about 4%, and preferably has a number average molecular weight Mn of about 2500 to about 25,000, more preferably about 3000 to about 10,000. Maleic anhydride is the preferred anhydride. Component (2) is present in an amount of about 5 to about 20 parts, preferably about 8 to about 16 parts, most preferably about 10 to about 14 parts, per hundred parts of the thermoplastic olefin.
Component (3) is an oxidized polyethylene wax having a melting point of less than 116xc2x0 C. and an acid number of less than 40. The oxidized wax is present in an amount of about 3 to about 20 parts, preferably about 5 to about 15 parts, most preferably about 5 to about 10 parts, per hundred parts of the thermoplastic polyolefin, whether or not the anhydride-grafted olefin polymer rubber (6) is present.
Component (4) is a functionalized polymer that is reactive with the anhydride groups of the grafted polymers (2) and, when present, components (6) and (7), selected from the group consisting of (a) an amine-terminated polyalkylene glycol, (b) a hydroxy-terminated polyolefin, (c) a hydroxy-terminated polybutadiene, (d) hydroxy-terminated olefin/alkylene oxide copolymers, (e) hydroxy-terminated polyalkylene oxides, (f) methoxy-terminated polyalkylene oxides, (g) amine-terminated olefin/alkylene oxide copolymers, and (h) mixtures thereof.
Component (4)(a), when present, is used in an amount of about 2 to about 6 parts, preferably about 2 to about 4 parts, per hundred parts of the thermoplastic olefin. The polyalkylene glycol can be, for example, polyethylene glycol, polypropylene glycol, copolymers of ethylene glycol and propylene glycol, poly(1,2-butylene glycol), and poly(tetramethylene glycol).
Component (4)(b), when present, is used in an amount of about 2 to about 6 parts, preferably about 2 to about 4 parts, per hundred parts of the thermoplastic olefin. Polyethylene is the preferred polyolefin, although polypropylene, polybutene, and copolymers of ethylene and another xcex1-olefin can also be used.
Component (4)(c), when present, is used in an amount of about 2 to about 6 parts, preferably about 2 to about 4 parts, per hundred parts of the thermoplastic olefin.
Component (4)(d), when present, is used in an amount of about 2 to about 8 parts, preferably about 2 to about 6 parts, per hundred parts of the thermoplastic olefin. An ethylene/ethylene oxide copolymer is preferred, although other copolymers such as ethylene/propylene oxide, propylene/ethylene oxide, butene/ethylene oxide, and butene/propylene oxide copolymers can also be used. The amount of alkylene oxide can be from about 10% to about 99.9%, preferably about 50% to about 98%, and most preferably about 75% to about 95%, based on 100% of the copolymer.
Component (4)(e), when present, is used in an amount of about 2 to about 8 parts, preferably about 2 to about 6 parts, per hundred parts of the thermoplastic olefin. Polyethylene oxide is preferred; however, polypropylene oxide, copolymers of ethylene oxide and propylene oxide, poly(1,2-butylene oxide), and poly(tetramethylene oxide) can also be used.
Component (4)(f), when present, is used in an amount of about 2 to about 8 parts, preferably about 2 to about 6 parts, per hundred parts of the thermoplastic olefin. Suitable polyalkylene oxides are those described for component (4)(e).
Component (4)(g), when present, is used in an amount of about 2 parts to about 8 parts, preferably about 2 to about 6 parts, per hundred parts of the thermoplastic olefin. The amount of alkylene oxide can be about 10% to about 99.9%, preferably about 50% to about 98%, and most preferably about 75% to about 95%. Examples of suitable olefin/alkylene oxide copolymers are described for component (4)(d).
When using a combination of functionalized polymers, the amount of each component can vary widely from about 0.1% to about 99.9% of each, based on the total amount of functionalized polymers. It is preferred that one component be present in an amount of  greater than 50%, preferably  greater than 60%, based on the total amount of functionalized polymers.
Instead of adding the functionalized polymer directly to the thermoplastic olefin, an adduct of the functionalized polymer and the anhydride-grafted polypropylene or ethylene/propylene copolymer can be prepared separately, then blended with the thermoplastic olefin.
Component (5) is an epichlorohydrin rubber; suitable epichlorohydrin rubbers include:
(5)(a) homopolymers of epichlorohydrin;
(5)(b) copolymers of epichlorohydrin with from about 1% to about 30% by mole of a saturated epoxy monomer or of an unsaturated epoxy monomer; and
(5)(c) terpolymers of epichlorohydrin with from about 1% to about 30% by mole of a saturated epoxy monomer and an unsaturated epoxy monomer; more preferably, the amount of such saturated epoxy monomer ranges from about 1 to about 10% by mole. Said epichlorohydrin rubbers generally have high molecular weights, density values ranging from about 1.35 g/cm3 to about 1.38 g/cm3, and a Mooney viscosity after 4 minutes at 212xc2x0 F. of from about 40 to about 80 ML. These rubbers can evidence certain degrees of crystallinity.
The epichlorohydrin rubbers may be prepared according to the methods known in the state of the art, for instance by polymerizing monomeric epichlorohydrin alone or together with one or more of the above-mentioned epoxy monomers in the presence of suitable catalysts, such as organometallic catalysts.
Typical saturated epoxy monomers include alkylene oxides, such ethylene oxide and propylene oxide, and typical unsaturated epoxy monomers include allylglycidyl ether.
The epichlorohydrin rubber is present in an amount of about 2 to about 20 parts, preferably about 5 to about 15 parts, most preferably about 10 parts, per hundred parts of the thermoplastic polyolefin.
Optional component (6) is an olefin polymer rubber grafted with an anhydride of an aliphatic xcex1,xcex2-unsaturated dicarboxylic acid and comprising a polymer of ethylene and a C3-8 xcex1-olefin, optionally containing about 0.5% to about 10% of a diene, preferably about 2% to about 6%. The anhydride-grafted polyolefin rubber has an ethylene content of about 30% to about 70%, preferably about 40% to about 60%, and has an anhydride content of at least 0.3% but less than 3%. Maleic anhydride is the preferred anhydride. When present, the anhydride-grafted rubber is used in an amount of about 5 to about 30 parts, preferably about 5 to about 15 parts, most preferably about 5 to about 12 parts, per hundred parts of the thermoplastic olefin.
Optional component (7) is an ethylene polymer grafted with an anhydride of an aliphatic xcex1,xcex1-unsaturated dicarboxylic acid and having an anhydride content of about 1% to about 16% by weight, preferably about 2% to about 13%, most preferably about 3% to about 13%. Maleic anhydride is the preferred anhydride. Ethylene homopolymer is preferred. However, copolymers containing 10% or less of an xcex1-olefin comonomer can also be used. The ethylene polymer preferably has a number average molecular weight Mn of about 500 to about 5000, preferably about 600 to about 2000, most preferably about 600 to about 1000. When component (6) is used, it is present in an amount of about 5 to about 20 parts, preferably about 5 to about 10 parts, per hundred parts of the thermoplastic olefin, provided that at least 5 parts of anhydride-grafted polypropylene or propylene copolymer and 3 parts of oxidized polyethylene wax per hundred parts of the thermoplastic olefin are also present.
Optional component (8) is a thermoplastic resin selected from the group consisting of:
(a) an hydrogenated polymer consisting essentially of terpene hydrocarbons, having a drop softening point greater than about 70xc2x0 C., and a number average molecular weight greater than about 500; and
(b) an hydrogenated polymer of styrene or alkyl-substituted styrene, having a number average molecular weight Mn ranging between about 600 and about 20,000.
Components (8)(a) are amorphous terpene hydrocarbons polymers, preferably having a drop softening point greater than about 100xc2x0 C. The softening point of the polymers is the temperature (xc2x0C.) at which the polymer changes from a rigid to a soft state, as determined by the Hercules drop method (described in the Hercules report entitled xe2x80x9cThe Hercules Drop Method for Determining the Softening Point of Rosins and Modified Rosinsxe2x80x9d. No. Herc. 400-431C, 1955). Components (8)(a) have preferably a number average molecular weight Mn greater than about 600 and a iodine value of less than about 50, and even more preferably a iodine value of less than about 15. The iodine value of the hydrocarbon polymers was determined in accordance with Method No. L 8a-57 of the American Oil Chemistry Society.
These amorphous terpene hydrocarbons polymers include the polymers produced by the hydrogenation of the resinous polymerization products obtained by the catalytic polymerization of mixed unsaturated monomers derived from the deep cracking of petroleum, as well as higher polymers obtained by polymerization and/or copolymerization of terpene hydrocarbons, followed by hydrogenation under pressure. Suitable components (8)(a) and the process for their preparation are described in U.S. Pat. No. 3,361,849, which is incorporated herein by reference.
Component (8)(b) is an hydrogenated polymer of styrene or alkyl-substituted styrene, having a number average molecular weight Mn ranging between about 600 and about 20,000.
By xe2x80x9chydrogenated polymer of styrene or alkyl-substituted styrenexe2x80x9d is meant a polymer selected from the group consisting of homopolymers of styrene and alkyl-substituted styrenes, copolymers of styrene and alkyl-substituted styrenes with each other, and copolymers of styrene and alkyl-substituted styrenes with other hydrocarbons having non-aromatic carbon-to-carbon unsaturations, said polymer being characterized by having at least 50% of its aromatic unsaturations hydrogenated, preferably at least 70% of its aromatic unsaturations hydrogenated, and a number average molecular weight Mn ranging from 600 to 20,000; said polymers have preferably a drop softening point between about 70xc2x0 and 170xc2x0 C.
Suitable components (8)(b) and the process for their preparation are described in U.S. Pat. No. 3,666,836, which is incorporated herein by reference.
When present, the thermoplastic resin (8) is used in an amount of about 5 to about 20 parts, preferably about 8 to about 6, most preferably about 10 to about 14 per hundred parts of the thermoplastic olefin.
Optional component (9) is an organic sulfonic acid salt of a group I or II metal of the Periodic Table of the Elements (IUPAC version).
Suitable organic sulfonic acids are sulfonic acids bearing a radical selected from saturated or unsaturated, linear or cyclic C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 alkylaryl and C7-C20 arylalkyl radicals, optionally containing one or more atoms belonging to groups 13-17 of the Periodic Table of the Elements (new IUPAC notation), such as B, N, P, Al, Si, Ge, O, S, Cl and F; more preferably, said radical is selected from the group consisting of trifluoromethyl, benzene, C1-C5 alkyl-benzene, naphthalene and C1-C5 alkyl-naphthalene.
Preferred metals belong to group I, and more preferably are selected from the group consisting of Li, Na and K.
When present, the organic sulfonic acid salt is used in an amount of about 0.1 to about 5 parts, preferably about 0.5 to about 1.5 per hundred parts of the thermoplastic olefin.
According to a preferred embodiment, the directly paintable polymer compositions of the present invention contain at least one of the components selected from the components (6), (7), (8) and (9) described above.
The composition of the present invention can also contain other conventional additives, for example, antioxidants; stabilizers; extender oils such as paraffinic and naphthenic oils; fillers such as CaCO3, talc, Al2O3, carbon black, and zinc oxide; or flame retardants.
If non-polymeric additives such as conductive or non-conductive carbon black are used, they are preferably added after the functionalized polymer has reacted with the anhydride-grafted polymers. The additives can also be added as a dispersion in a polymer, preferably an olefin polymer.
The compounding or melt blending of the components of the composition can be carried out on an open roll, in an internal mixer (Banbury or Haake mixers), or in single-screw or twin screw extruders.
The compositions of this invention can be formed in any way, such as by extrusion, compression molding, and thermoforming; injection molding is preferred. They can also be co-extruded or co-injection molded with other polyolefin materials such as propylene homopolymers, copolymers, and graft copolymers, ethylene homopolymers and copolymers, or thermoplastic olefins such as those described previously. They can also be co-extruded or co-injection molded with olefin-based dynamically vulcanized elastomers or olefin-compatible thermoplastic elastomers such as styrene/butadiene copolymers.
The compositions of the present invention show an increased electrical conductivity; in fact, the volume resistivity, determined by ASTM D257 method, is preferably lower than about 1xc2x71015 ohmxc2x7cm, and more preferably lower than about 5xc2x71014 ohmxc2x7cm. As described above, the epichlorohydrin rubber component in the compositions of the invention leads to a significant electrical conductivity increase, without detrimental impact on the chemical/physical properties of the thermoplastic compositions; this significant increase is critical for reaching electrical dissipating molded articles.
The compositions according to the present invention can be used to make a variety of articles, such as automotive fascia, rocker panels, spoilers, bumpers and other vehicle exterior or interior trim components. Since the compositions of the present invention have an increased electrical conductivity, they are particularly suitable for articles which are subject to painting.
Paint Adhesion Test and Durability Test
The specimens for testing were prepared using a pin-gated mold rather than the fan-gated mold typically used for molding thermoplastic olefins. Durability depends upon the paint thickness; the thicker the paint or film, the better the durability. In the following examples and comparative examples only one coat of paint was used with an approximately 1.2 mil (3.048xc2x710xe2x88x925 m) film thickness, which is a very severe test. A typical durability test used in the automotive industry also employs a top coat that has a low coefficient of friction, which reduces the severity of the test; no top coat was used in the following examples and comparative examples.
The samples for testing were prepared by dry blending the ingredients and reactive mixing in a twin screw extruder at a temperature of 450xc2x0 F. (232xc2x0 C.) and pelletizing the resultant material. The pellets were injection molded into disks that were painted with about a 1.2 to 2 mil (3.048xc2x710xe2x88x925 to 5.0xc2x710xe2x88x925 m) thick coating using DuPont 872 white paint and cured at 250xc2x0 F. (121xc2x0 C.) for thirty minutes. A lattice pattern of squares with each square about xc2xc inch in size was scribed on the painted disk at the end opposite the gate area of the disk. Adhesive tape (3M 898) was pressed onto the paint and pulled off to test the amount of paint removed or the paint adhesion. The % failure was recorded as the % of the squares removed by the tape after one pull. The durability was determined by using a Taber abrader with a type C scuffing head assembly and a one pound load. The painted disk was placed in an oven at 70xc2x0 C. for one hour, removed and placed on the platform of the abrader. The scuffing head was placed in contact with the painted surface and the disk was rotated for a specified number of cycles. The amount of paint removed from the complete circumference subtended by the scuffing head was recorded as the % failure. The criteria set for acceptable paint adhesion were  less than 50% failure in the gate area of the disk and  less than 10% in the area opposite the gate area after the first pull, and  less than 85% failure in the gate area and  less than 50% in the area opposite the gate after the fifth pull.
The criteria for satisfactory durability was  less than 50% failure after 100 cycles.
Volume Resistivity Test
Volume Resistivity was measured according to ASTM D257 method, with a time of electrification equal to 5 seconds; acceptable values for volume resistivity are lower than 1xc2x71015 ohmxc2x7cm.